1. Field of Invention
The invention relates to sulfur modified coal compositions in which coal-derived asphaltenes are used to produce asphaltic pitch-like compositions suitable for use as binder materials in the construction of asphalt paving structures.
2. Description of Prior Art
The use of sulfur in pitches, tars, bitumens and asphalts is well known in the art. One or more properties of such compositions can be improved by the presence of sulfur particularly when the composition is used in the surfacing of roads. As described in U.S. Pat. No. 3,738,853, sulfur-asphalt pavements are prepared by casting sulfur-asphalt-aggregate mixes. In U.S. Pat. No. 3,960,585 cast sulfur-asphalt compositions are prepared by mixing and/or heating sulfur and asphalt at elevated temperatures in the presence of hydrogen sulfide suppressants such as free radical inhibitors and redox catalysts. U.S. Pat. No. 3,970,468 discloses emulsions of sulfur in asphalt, bitumen or tar wherein the sulfur is dispersed in the form of particles not exceeding 10 microns by melting a mixture of sulfur and hydrocarbon above 120.degree. C. and subjecting the mixture to a dispersing agitation.
Other references to the use of sulfur in various asphaltic products include the use of sulfur monochloride in admixture with olefin polymers and petroleum residuum as disclosed in U.S. Pat. No. 3,093,610 and compositions obtained by heating a mixture of bitumen, olefin polymer, sulfur and a sulfur-containing vulcanization accelerator as described in U.S. Pat. No. 3,992,340. U.S. Pat. No. 3,960,793 discloses blending "reject polypropylene" with asphalts to product adhesives and molding compositions. The asphalts may be treated with sulfur or halogen-containing materials to increase their consistency.